Autophagy facilitates TLR4- and TLR3-triggered migration and invasion of lung cancer cells through the promotion of TRAF6 ubiquitination

NADPH oxidase 1-dependent ROS is crucial for TLR4 signaling to promote tumor metastasis of non-small cell lung cancer

Recent evidence demonstrated an enhanced metastasis of non-small cell lung cancer (NSCLC) cells induced by lipopolysaccharide (LPS) stimulation, which reflected an important role of inflammation in tumor progression. However, the underlying mechanisms still remain unclear. Here, we evaluated the potential role of reactive oxygen species (ROS) in Toll-like receptor 4 (TLR4) signaling enhanced NSCLC metastasis. NSCLC cells were isolated from clinical surgical tissues. We found that LPS stimulation of NSCLC cells facilitates their metastasis that was accompanied by increased ROS production and could be abrogated by ROS inhibition. NADPH oxidase was essential for TLR4 signaling-enhanced NSCLC metastasis. Elevated NADPH oxidase 1 (NOX1) expression by LPS stimulation was observed. Blockade of NOX1 with ML171 alleviated enhanced NSCLC metastasis by TLR4 signaling. Enforced NOX1 expression promoted TLR4 signaling-enhanced NSCLC metastasis, while decreased NOX1 expression inhibited TLR4 signaling-enhanced NSCLC metastasis. Further, NOX1 could regulate the expression of CXCR4 and matrix metallopeptidase 9 (MMP9) in NSCLC cells. NOX1 expression in tumor tissues was correlated with TLR4 expression and clinical stages in NSCLC patients. Finally, inhibition of NOX1/ROS prevented enhanced lung tumor burdens of NSCLC by LPS-induced acute lung infection. Our findings demonstrated a crucial role of NOX1-dependent ROS for TLR4 signaling to enhance the metastasis of NSCLC, which could further the understanding of NSCLC pathogenesis and helpful for developing novel therapeutics for NSCLC.

Autophagy in SDF-1α-mediated DPSC migration and pulp regeneration

Critical morphological requirements for pulp regeneration are tissues replete with vascularisation, neuron formation, and dentin deposition. Autophagy was recently shown to be related to angiogenesis, neural differentiation, and osteogenesis. The present study aimed to investigate the involvement of autophagy in stromal cell-derived factor-1α (SDF-1α)-mediated dental pulp stem cell (DPSC) migration and pulp regeneration, and identify its presence during pulp revascularisation of pulpectomised dog teeth with complete apical closure. In vitro studies showed that SDF-1α enhanced DPSCs migration and optimised focal adhesion formation and stress fibre assembly, which were accompanied by autophagy. Moreover, autophagy inhibitors significantly suppressed, whereas autophagy activator substantially augmented SDF-1α-stimulated DPSCs migration. Furthermore, after ectopic transplantation of tooth fragment/silk fibroin scaffold with DPSCs into nude mice, pulp-like tissues with vascularity, well-organised fibrous matrix formation, and new dentin deposition along the dentinal wall were generated in SDF-1α-loaded samples accompanied by autophagy. More importantly, in a pulp revascularisation model in situ, SDF-1α-loaded silk fibroin scaffolds improved the de novo ingrowth of pulp-like tissues in pulpectomised mature dog teeth, which correlated with the punctuated LC3 and Atg5 expressions, indicating autophagy. Our findings provide novel insights into the pulp regeneration mechanism, and SDF-1α shows promise for future clinical application in pulp revascularisation.

Recent advances in the role of toll-like receptors and TLR agonists in immunotherapy for human glioma

Gliomas are extremely aggressive brain tumors with a very poor prognosis. One of the more promising strategies for the treatment of human gliomas is targeted immunotherapy where antigens that are unique to the tumors are exploited to generate vaccines. The approach, however, is complicated by the fact that human gliomas escape immune surveillance by creating an immune suppressed microenvironment. In order to oppose the glioma imposed immune suppression, molecules and pathways involved in immune cell maturation, expansion, and migration are under intensive clinical investigation as adjuvant therapy. Toll-like receptors (TLRs) mediate many of these functions in immune cell types, and TLR agonists, thus, are currently primary candidate molecules to be used as important adjuvants in a variety of cancers. In animal models for glioma, TLR agonists have exhibited antitumor properties by facilitating antigen presentation and stimulating innate and adaptive immunity. In clinical trials, several TLR agonists have achieved survival benefit, and many more trials are recruiting or ongoing. However, a second complicating factor is that TLRs are also expressed on cancer cells where they can participate instead in a variety of tumor promoting activities including cell growth, proliferation, invasion, migration, and even stem cell maintenance. TLR agonists can, therefore, possibly play dual roles in tumor biology. Here, how TLRs and TLR agonists function in glioma biology and in anti-glioma therapies is summarized in an effort to provide a current picture of the sophisticated relationship of glioma with the immune system and the implications for immunotherapy.

Chloroquine inhibits MGC803 gastric cancer cell migration via the Toll-like receptor 9/nuclear factor kappa B signaling pathway

Stimulation of Toll‑like receptor 9 (TLR9) has been associated with invasion in various types of cancer cell in vitro. The present study aimed to evaluate the expression of TLR9 in MGC803 gastric cancer cells and investigate the effect of a non‑specific TLR9 inhibitor, chloroquine (CQ), on MGC803 cell migration via the TLR9/nuclear factor kappa B (NFκB) signaling pathway. The expression of TLR9 was investigated using reverse transcription polymerase chain reaction (RT‑PCR), flow cytometry and western blot analysis. The effects of CQ on MGC803 cell proliferation were measured by MTT colorimetric assay. The mRNA expression levels of cyclooxygenase‑2 (COX‑2), matrix metalloproteinase (MMP)‑2, MMP‑7 and NFκB p65 were evaluated by RT‑PCR in MGC803 cells stimulated by various concentrations of CQ. The migration of gastric cancer cells treated with CQ at 12, 24 and 36 h was measured by wound healing assay. The results indicated that MGC803 cells expressed TLR9 and that CQ had anti‑proliferative effects on MGC803 cells and inhibited mRNA expression of COX‑2, MMP‑2, MMP‑7 and NFκB p65 (P<0.05). Furthermore, CQ inhibited the bioactivity of NFκB p65 and prevented the migration of MGC803 cells in a dose‑dependent manner (P<0.05). In conclusion, the results indicated that the TLR9/NFκB signaling pathway was involved in gastric cancer cell migration and that CQ had anti‑tumor activity.

Cancer-derived immunoglobulin G promotes LPS-induced proinflammatory cytokine production via binding to TLR4 in cervical cancer cells

Numerous studies have shown that various cancer cells express immunoglobulin G (IgG). However, the function of cancer-derived IgG and the underlying mechanism remain unclear. In this study, we demonstrated that IgG expression was significantly altered after exposure to LPS in cervical cancer cells, suggesting that IgG was potentially involved in regulation of TLR4 signaling. Reduction of IgG attenuated LPS-induced proinflammatory cytokine production. The phosphorylation levels of NF-κB and MAPK were consistently suppressed by knockdown of IgG, which in turn impaired NF-κB nuclear translocation and the activity of NF-κB responsive element. Furthermore, we found that IgG was recruited to TLR4 in the cytoplasm after LPS stimulation, and IgG silencing inhibited LPS-initiated proinflammatory cytokine production through downregulating TLR4 expression. Similar results were obtained in a mouse model of endotoxemia and human tissues. Taken together, our findings demonstrate that IgG is a positive regulator of LPS-induced proinflammatory cytokine production by binding to TLR4 and enhancing its expression. TLR4 signaling plays a positive role in the development of many inflammation induced cancers such as cervical cancer. Our study strongly indicates that IgG may promote cervical cancer cell proliferation through enhancing TLR4 signaling. IgG may be a novel therapeutic target in treating inflammation mediated cancers.

Cellular and metabolic functions for autophagy in cancer cells

Autophagy is a lysosomal degradation pathway that acts as a dynamic regulator of tumorigenesis. Specifically, autophagy has been shown to impede early cancer development while facilitating advanced tumor progression. Recent studies have uncovered several tumor-promoting functions for autophagy; these include the maintenance of multiple metabolic pathways critical for aggressive tumor growth and the promotion of tumor cell survival downstream of the unfolded protein response. Furthermore, autophagy supports anoikis resistance and cancer cell invasion. At the same time, because autophagy cargo receptors, which are essential for selective autophagy, lie upstream of diverse cancer-promoting signaling pathways, they may profoundly influence how alterations in autophagy affect tumor development. This review focuses on how these tumor cell autonomous functions of autophagy broadly impact tumorigenesis.

Autophagy: an adaptive metabolic response to stress shaping the antitumor immunity

Several environmental-associated stress conditions, including hypoxia, starvation, oxidative stress, fast growth and cell death suppression, modulate both cellular metabolism and autophagy to enable cancer cells to rapidly adapt to environmental stressors, maintain proliferation and evade therapies. It is now widely accepted that autophagy is essential to support cancer cell growth and metabolism and that metabolic reprogramming in cancer can also favor autophagy induction. Therefore, this complex interplay between autophagy and tumor cell metabolism will provide unique opportunities to identify new therapeutic targets. As the regulation of the autophagic activity is related to metabolism, it is important to elucidate the exact molecular mechanism which drives it and the functional consequence of its activation in the context of cancer therapy. In this review, we will summarize the role of autophagy in shaping the cellular response to an abnormal tumor microenvironment and discuss some recent results on the molecular mechanism by which autophagy plays such a role in the context of the anti-tumor immune response. We will also describe how autophagy activation can behave as a double-edged sword, by activating the immune response in some circumstances, and impairing the anti-tumor immunity in others. These findings imply that defining the precise context-specific role for autophagy in cancer is critical to guide autophagy-based therapeutics which are becoming key strategies to overcome tumor resistance to therapies.

Ablation of Akt2 protects against lipopolysaccharide-induced cardiac dysfunction: role of Akt ubiquitination E3 ligase TRAF6

Lipopolysaccharide (LPS), an essential component of the outer membrane of Gram-negative bacteria, plays a pivotal role in myocardial anomalies in sepsis. Recent evidence has depicted a role of Akt in LPS-induced cardiac sequelae although little information is available with regard to the contribution of Akt isoforms in the endotoxin-induced cardiac dysfunction. This study examined the effect of Akt2 knockout on LPS-induced myocardial contractile dysfunction and the underlying mechanism(s) with a focus on TNF receptor-associated factor 6 (TRAF6). Echocardiographic properties and cardiomyocyte contractile function [peak shortening (PS), maximal velocity of shortening/relengthening, time-to-PS, time-to-90% relengthening] were examined in wild-type and Akt2 knockout mice following LPS challenge (4mg/kg, 4h). LPS challenge enlarged LV end systolic diameter, reduced fractional shortening and cardiomyocyte contractile capacity, prolonged TR90, promoted apoptosis, upregulated caspase-3/-12, ubiquitin, and the ubiquitination E3 ligase TRAF6 as well as decreased mitochondrial membrane potential without affecting the levels of TNF-α, toll-like receptor 4 and the mitochondrial protein ALDH2. Although Akt2 knockout failed to affect myocardial function, apoptosis, and ubiquitination, it significantly attenuated or mitigated LPS-induced changes in cardiac contractile and mitochondrial function, apoptosis and ubiquitination but not TRAF6. LPS facilitated ubiquitination, phosphorylation of Akt, GSK3β and p38, the effect of which with the exception of p38 was ablated by Akt2 knockout. TRAF6 inhibitory peptide or RNA silencing significantly attenuated LPS-induced Akt2 ubiquitination, cardiac contractile anomalies and apoptosis. These data collectively suggested that TRAF6 may play a pivotal role in mediating LPS-induced cardiac injury via Akt2 ubiquitination.